This invention relates to methods and apparatus for stripping end portions of wires and cables, and more particularly to stripping the various layers of insulation and conductive shield material from a center conductor cable such as coaxial cable and the like.
Coaxial cable such as those used in transmitting data, television signals and computer network signals usually have a center conductor encapsulated in a dielectric material that is overlaid with a conducting shielding layer, all of which is usually encased in an outer protective jacket. In order to connect one end of a cable to another, a termination must be fixed mechanically and electrically to the conductive portions of the cable to permit connection to terminal strips and other cable ends. Independent electrical connections to both the center conductor and electrically shielding layers must be established to permit functioning of the cable.
Insulations and shields are of wide varieties and types of materials and pose a significant problem in the industry in their removal for good electrical connections. While stripping of these materials may be done manually, it is a very tedious and difficult job and frequently the conductor or shield is either nicked or severed in an unwanted fashion so as to seriously affect the electrical properties thereof. This is particularly important in the high-speed data transmission type of cable where conductors tend, at high frequencies, to carry most of their electrical information on the surface of the conductor and even a small scratch or nick can seriously interrupt the flow of electrical information.
For this reason, power operated rotary strippers have been developed for accurately and quickly stripping the ends of coaxial type wires and cables. These have generally involved apparatus such as that shown in U.S. Pat. No. 3,074,301 to Carpenter which has one or two pivotally mounted blades adapted to pivot out of the way as the wire is inserted into the device and then to cam into single cut cutting position as the cutting head is rotated and the wire end is withdrawn from the device. These devices have generally worked well for the removal of a single segment of the outer covering and have usually necessitated the use of multiple devices to remove the several layers of different material from a conductor.
Attempts have been made to remove two or more segments from the end of a multi-layered conductor, but they have generally encountered the insurmountable problem of the removal from the cutting device of the one or more "slugs" remaining after cutting the various layers of the wire coverings. Two and three bladed strippers have been attempted, however, none have been successful because of continual jamming caused by the "slugs" hanging up between the knives within the rotary cutting head.